In many circuit applications a simple programmable active high or active low level must be established. Preferably the creation of the active high or active low signal is implemented with an arrangement requiring a minimum of power. Typically, this arrangement has been established by using a resistor bridge wherein one portion, for instance, the upper portion of the bridge comprises a resistor and the lower portion of the bridge is implemented with a single fuse. In order to program the device all that need be done is to either permit the fuse to remain intact in which case the logic level would be low due to the relatively low resistance of the conducting fuse relative to the resistor. Alternatively, if the fuse were blown, the relative resistance of the blown fuse would be significantly greater than the resistance of the resistor and the device would be programmed high. To provide a lower power and more reliable programming arrangement it is necessary to provide a very significant decrease in the current used by the circuit while maintaining a large relative difference in resistance between the two branches of the resistive bridge. While the prior resistive bridge arrangement is relatively easy to implement, it has several drawbacks when adopted in an MOS application. The standby current of this device is unreasonably high for low power applications and the need for a resistor of significant resistance results in the use of a substantial amount of area on the die. In a CMOS application where power consumption is a primary concern, the prior resistor bridge arrangement causes an excessive current drain, particularly for battery powered applications.
Another aspect of the present invention relates to problems which have existed with the prior resistive bridge arrangement including the failure of the fuse to remain in a blown state due to electrical conduction and refabrication of a conductor at the fuse location, partial blowing of the fuse causing increased resistance yet maintaining enough conductivity to prevent the resistive bridge from establishing a definite logic level and finally, the failure of the fuse to blow under programming level voltage and current resulting in an incorrectly programmed device. While no one of these problems is so significant as to render the prior arrangement unacceptable, the combination of these problems does result in a decrease in the number of acceptable circuits generated in the fabrication process. As a result of the above problems, the defective circuits generally render the entire device inoperative. Thus, the elimination of any of the above problems results in a very substantial savings in the manufacture of products utilizing such circuits. Ideally, the elimination of such problems should be easily implemented and inexpensive.